/**
* @file
* NetBIOS name service responder
*/

/**
 * @defgroup netbiosns NETBIOS responder
 * @ingroup apps
 *
 * This is an example implementation of a NetBIOS name server.
 * It responds to name queries for a configurable name.
 * Name resolving is not supported.
 *
 * Note that the device doesn't broadcast it's own name so can't
 * detect duplicate names!
 */

/*
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Modifications by Ray Abram to respond to NetBIOS name requests when Incoming name = *
 * - based on code from "https://github.com/esp8266/Arduino/commit/1f7989b31d26d7df9776a08f36d685eae7ac8f99"
 * - with permission to relicense to BSD from original author:
 *   http://www.xpablo.cz/?p=751#more-751
 */

#include "lwip/apps/netbiosns.h"

#if LWIP_IPV4 && LWIP_UDP  /* don't build if not configured for use in lwipopts.h */

#include "lwip/def.h"
#include "lwip/udp.h"
#include "lwip/ip.h"
#include "lwip/netif.h"
#include "lwip/prot/iana.h"

#include <string.h>

/** size of a NetBIOS name */
#define NETBIOS_NAME_LEN 16

/** The Time-To-Live for NetBIOS name responds (in seconds)
 * Default is 300000 seconds (3 days, 11 hours, 20 minutes) */
#define NETBIOS_NAME_TTL 300000u

/** NetBIOS header flags */
#define NETB_HFLAG_RESPONSE           0x8000U
#define NETB_HFLAG_OPCODE             0x7800U
#define NETB_HFLAG_OPCODE_NAME_QUERY  0x0000U
#define NETB_HFLAG_AUTHORATIVE        0x0400U
#define NETB_HFLAG_TRUNCATED          0x0200U
#define NETB_HFLAG_RECURS_DESIRED     0x0100U
#define NETB_HFLAG_RECURS_AVAILABLE   0x0080U
#define NETB_HFLAG_BROADCAST          0x0010U
#define NETB_HFLAG_REPLYCODE          0x0008U
#define NETB_HFLAG_REPLYCODE_NOERROR  0x0000U

/* NetBIOS question types */
#define NETB_QTYPE_NB                 0x0020U
#define NETB_QTYPE_NBSTAT             0x0021U

/** NetBIOS name flags */
#define NETB_NFLAG_UNIQUE             0x8000U
#define NETB_NFLAG_NODETYPE           0x6000U
#define NETB_NFLAG_NODETYPE_HNODE     0x6000U
#define NETB_NFLAG_NODETYPE_MNODE     0x4000U
#define NETB_NFLAG_NODETYPE_PNODE     0x2000U
#define NETB_NFLAG_NODETYPE_BNODE     0x0000U

#define NETB_NFLAG_NAME_IN_CONFLICT   0x0800U /* 1=Yes, 0=No */
#define NETB_NFLAG_NAME_IS_ACTIVE     0x0400U /* 1=Yes, 0=No */
#define NETB_NFLAG_NAME_IS_PERMANENT  0x0200U /* 1=Yes (Name is Permanent Node Name), 0=No */

/** NetBIOS message header */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct netbios_hdr {
    PACK_STRUCT_FIELD(u16_t trans_id);
    PACK_STRUCT_FIELD(u16_t flags);
    PACK_STRUCT_FIELD(u16_t questions);
    PACK_STRUCT_FIELD(u16_t answerRRs);
    PACK_STRUCT_FIELD(u16_t authorityRRs);
    PACK_STRUCT_FIELD(u16_t additionalRRs);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif

/** NetBIOS message question part */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct netbios_question_hdr {
    PACK_STRUCT_FLD_8(u8_t  nametype);
    PACK_STRUCT_FLD_8(u8_t  encname[(NETBIOS_NAME_LEN * 2) + 1]);
    PACK_STRUCT_FIELD(u16_t type);
    PACK_STRUCT_FIELD(u16_t cls);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif

/** NetBIOS message name part */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct netbios_name_hdr {
    PACK_STRUCT_FLD_8(u8_t  nametype);
    PACK_STRUCT_FLD_8(u8_t  encname[(NETBIOS_NAME_LEN * 2) + 1]);
    PACK_STRUCT_FIELD(u16_t type);
    PACK_STRUCT_FIELD(u16_t cls);
    PACK_STRUCT_FIELD(u32_t ttl);
    PACK_STRUCT_FIELD(u16_t datalen);
    PACK_STRUCT_FIELD(u16_t flags);
    PACK_STRUCT_FLD_S(ip4_addr_p_t addr);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif

/** NetBIOS message */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct netbios_resp {
    struct netbios_hdr      resp_hdr;
    struct netbios_name_hdr resp_name;
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif

/** The NBNS Structure Responds to a Name Query */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct netbios_answer {
    struct netbios_hdr      answer_hdr;
    /** the length of the next string */
    PACK_STRUCT_FIELD(u8_t  name_size);
    /** WARNING!!! this item may be of a different length (we use this struct for transmission) */
    PACK_STRUCT_FLD_8(u8_t  query_name[(NETBIOS_NAME_LEN * 2) + 1]);
    PACK_STRUCT_FIELD(u16_t packet_type);
    PACK_STRUCT_FIELD(u16_t cls);
    PACK_STRUCT_FIELD(u32_t ttl);
    PACK_STRUCT_FIELD(u16_t data_length);
#define OFFSETOF_STRUCT_NETBIOS_ANSWER_NUMBER_OF_NAMES 56
    /** number of names */
    PACK_STRUCT_FLD_8(u8_t  number_of_names);
    /** node name */
    PACK_STRUCT_FLD_8(u8_t  answer_name[NETBIOS_NAME_LEN]);
    /** node flags */
    PACK_STRUCT_FIELD(u16_t answer_name_flags);
    /** Unit ID */
    PACK_STRUCT_FLD_8(u8_t  unit_id[6]);
    /** Jumpers */
    PACK_STRUCT_FLD_8(u8_t  jumpers);
    /** Test result */
    PACK_STRUCT_FLD_8(u8_t  test_result);
    /** Version number */
    PACK_STRUCT_FIELD(u16_t version_number);
    /** Period of statistics */
    PACK_STRUCT_FIELD(u16_t period_of_statistics);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_crcs);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_alignment_errors);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_collisions);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_send_aborts);
    /** Statistics */
    PACK_STRUCT_FIELD(u32_t number_of_good_sends);
    /** Statistics */
    PACK_STRUCT_FIELD(u32_t number_of_good_receives);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_retransmits);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_no_resource_condition);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_free_command_blocks);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t total_number_of_command_blocks);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t max_total_number_of_command_blocks);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t number_of_pending_sessions);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t max_number_of_pending_sessions);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t max_total_sessions_possible);
    /** Statistics */
    PACK_STRUCT_FIELD(u16_t session_data_packet_size);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif

#ifdef NETBIOS_LWIP_NAME
#define NETBIOS_LOCAL_NAME NETBIOS_LWIP_NAME
#else
static char netbiosns_local_name[NETBIOS_NAME_LEN];
#define NETBIOS_LOCAL_NAME netbiosns_local_name
#endif

static struct udp_pcb* netbiosns_pcb;

/** Decode a NetBIOS name (from packet to string) */
static int
netbiosns_name_decode(char* name_enc, char* name_dec, int name_dec_len)
{
    char* pname;
    char  cname;
    char  cnbname;
    int   idx = 0;

    LWIP_UNUSED_ARG(name_dec_len);

    /* Start decoding netbios name. */
    pname  = name_enc;
    for (;;) {
        /* Every two characters of the first level-encoded name
         * turn into one character in the decoded name. */
        cname = *pname;
        if (cname == '\0') {
            break;  /* no more characters */
        }
        if (cname == '.') {
            break;  /* scope ID follows */
        }
        if (!lwip_isupper(cname)) {
            /* Not legal. */
            return -1;
        }
        cname -= 'A';
        cnbname = cname << 4;
        pname++;

        cname = *pname;
        if (!lwip_isupper(cname)) {
            /* Not legal. */
            return -1;
        }
        cname -= 'A';
        cnbname |= cname;
        pname++;

        /* Do we have room to store the character? */
        if (idx < NETBIOS_NAME_LEN) {
            /* Yes - store the character. */
            name_dec[idx++] = (cnbname != ' ' ? cnbname : '\0');
        }
    }

    return 0;
}


/** NetBIOS Name service recv callback */
static void
netbiosns_recv(void* arg, struct udp_pcb* upcb, struct pbuf* p, const ip_addr_t* addr, u16_t port)
{
    LWIP_UNUSED_ARG(arg);

    /* if packet is valid */
    if (p != NULL) {
        char   netbios_name[NETBIOS_NAME_LEN + 1];
        struct netbios_hdr*          netbios_hdr          = (struct netbios_hdr*)p->payload;
        struct netbios_question_hdr* netbios_question_hdr = (struct netbios_question_hdr*)(netbios_hdr + 1);

        /* is the packet long enough (we need the header in one piece) */
        if (p->len < (sizeof(struct netbios_hdr) + sizeof(struct netbios_question_hdr))) {
            /* packet too short */
            pbuf_free(p);
            return;
        }
        /* we only answer if we got a default interface */
        if (netif_default != NULL) {
            /* @todo: do we need to check answerRRs/authorityRRs/additionalRRs? */
            /* if the packet is a NetBIOS name query question */
            if (((netbios_hdr->flags & PP_NTOHS(NETB_HFLAG_OPCODE)) == PP_NTOHS(NETB_HFLAG_OPCODE_NAME_QUERY)) &&
                    ((netbios_hdr->flags & PP_NTOHS(NETB_HFLAG_RESPONSE)) == 0) &&
                    (netbios_hdr->questions == PP_NTOHS(1))) {
                /* decode the NetBIOS name */
                netbiosns_name_decode((char*)(netbios_question_hdr->encname), netbios_name, sizeof(netbios_name));
                /* check the request type */
                if (netbios_question_hdr->type == PP_HTONS(NETB_QTYPE_NB)) {
                    /* if the packet is for us */
                    if (lwip_strnicmp(netbios_name, NETBIOS_LOCAL_NAME, sizeof(NETBIOS_LOCAL_NAME)) == 0) {
                        struct pbuf* q;
                        struct netbios_resp* resp;

                        q = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct netbios_resp), PBUF_RAM);
                        if (q != NULL) {
                            resp = (struct netbios_resp*)q->payload;

                            /* prepare NetBIOS header response */
                            resp->resp_hdr.trans_id      = netbios_hdr->trans_id;
                            resp->resp_hdr.flags         = PP_HTONS(NETB_HFLAG_RESPONSE |
                                                                    NETB_HFLAG_OPCODE_NAME_QUERY |
                                                                    NETB_HFLAG_AUTHORATIVE |
                                                                    NETB_HFLAG_RECURS_DESIRED);
                            resp->resp_hdr.questions     = 0;
                            resp->resp_hdr.answerRRs     = PP_HTONS(1);
                            resp->resp_hdr.authorityRRs  = 0;
                            resp->resp_hdr.additionalRRs = 0;

                            /* prepare NetBIOS header datas */
                            MEMCPY( resp->resp_name.encname, netbios_question_hdr->encname, sizeof(netbios_question_hdr->encname));
                            resp->resp_name.nametype     = netbios_question_hdr->nametype;
                            resp->resp_name.type         = netbios_question_hdr->type;
                            resp->resp_name.cls          = netbios_question_hdr->cls;
                            resp->resp_name.ttl          = PP_HTONL(NETBIOS_NAME_TTL);
                            resp->resp_name.datalen      = PP_HTONS(sizeof(resp->resp_name.flags) + sizeof(resp->resp_name.addr));
                            resp->resp_name.flags        = PP_HTONS(NETB_NFLAG_NODETYPE_BNODE);
                            ip4_addr_copy(resp->resp_name.addr, *netif_ip4_addr(netif_default));

                            /* send the NetBIOS response */
                            udp_sendto(upcb, q, addr, port);

                            /* free the "reference" pbuf */
                            pbuf_free(q);
                        }
                    }
#if LWIP_NETBIOS_RESPOND_NAME_QUERY
                }
                else if (netbios_question_hdr->type == PP_HTONS(NETB_QTYPE_NBSTAT)) {
                    /* if the packet is for us or general query */
                    if (!lwip_strnicmp(netbios_name, NETBIOS_LOCAL_NAME, sizeof(NETBIOS_LOCAL_NAME)) ||
                            !lwip_strnicmp(netbios_name, "*", sizeof(NETBIOS_LOCAL_NAME))) {
                        /* general query - ask for our IP address */
                        struct pbuf* q;
                        struct netbios_answer* resp;

                        q = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct netbios_answer), PBUF_RAM);
                        if (q != NULL) {
                            /* buffer to which a response is compiled */
                            resp = (struct netbios_answer*) q->payload;

                            /* Init response to zero, especially the statistics fields */
                            memset(resp, 0, sizeof(*resp));

                            /* copy the query to the response ID */
                            resp->answer_hdr.trans_id        = netbios_hdr->trans_id;
                            /* acknowledgment of termination */
                            resp->answer_hdr.flags           = PP_HTONS(NETB_HFLAG_RESPONSE | NETB_HFLAG_OPCODE_NAME_QUERY | NETB_HFLAG_AUTHORATIVE);
                            /* resp->answer_hdr.questions       = PP_HTONS(0); done by memset() */
                            /* serial number of the answer */
                            resp->answer_hdr.answerRRs       = PP_HTONS(1);
                            /* resp->answer_hdr.authorityRRs    = PP_HTONS(0); done by memset() */
                            /* resp->answer_hdr.additionalRRs   = PP_HTONS(0); done by memset() */
                            /* we will copy the length of the station name */
                            resp->name_size                  = netbios_question_hdr->nametype;
                            /* we will copy the queried name */
                            MEMCPY(resp->query_name, netbios_question_hdr->encname, (NETBIOS_NAME_LEN * 2) + 1);
                            /* NBSTAT */
                            resp->packet_type                = PP_HTONS(0x21);
                            /* Internet name */
                            resp->cls                        = PP_HTONS(1);
                            /* resp->ttl                        = PP_HTONL(0); done by memset() */
                            resp->data_length                = PP_HTONS(sizeof(struct netbios_answer) - offsetof(struct netbios_answer, number_of_names));
                            resp->number_of_names            = 1;

                            /* make windows see us as workstation, not as a server */
                            memset(resp->answer_name, 0x20, NETBIOS_NAME_LEN - 1);
                            /* strlen is checked to be < NETBIOS_NAME_LEN during initialization */
                            MEMCPY(resp->answer_name, NETBIOS_LOCAL_NAME, strlen(NETBIOS_LOCAL_NAME));

                            /* b-node, unique, active */
                            resp->answer_name_flags          = PP_HTONS(NETB_NFLAG_NAME_IS_ACTIVE);

                            /* Set responder netif MAC address */
                            SMEMCPY(resp->unit_id, ip_current_input_netif()->hwaddr, sizeof(resp->unit_id));

                            udp_sendto(upcb, q, addr, port);
                            pbuf_free(q);
                        }
                    }
#endif /* LWIP_NETBIOS_RESPOND_NAME_QUERY */
                }
            }
        }
        /* free the pbuf */
        pbuf_free(p);
    }
}

/**
 * @ingroup netbiosns
 * Init netbios responder
 */
void
netbiosns_init(void)
{
    /* LWIP_ASSERT_CORE_LOCKED(); is checked by udp_new() */
#ifdef NETBIOS_LWIP_NAME
    LWIP_ASSERT("NetBIOS name is too long!", strlen(NETBIOS_LWIP_NAME) < NETBIOS_NAME_LEN);
#endif

    netbiosns_pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
    if (netbiosns_pcb != NULL) {
        /* we have to be allowed to send broadcast packets! */
        ip_set_option(netbiosns_pcb, SOF_BROADCAST);
        udp_bind(netbiosns_pcb, IP_ANY_TYPE, LWIP_IANA_PORT_NETBIOS);
        udp_recv(netbiosns_pcb, netbiosns_recv, netbiosns_pcb);
    }
}

#ifndef NETBIOS_LWIP_NAME
/**
 * @ingroup netbiosns
 * Set netbios name. ATTENTION: the hostname must be less than 15 characters!
 *                              the NetBIOS name spec says the name MUST be upper case, so incoming name is forced into uppercase :-)
 */
void
netbiosns_set_name(const char* hostname)
{
    size_t i;
    size_t copy_len = strlen(hostname);
    LWIP_ASSERT_CORE_LOCKED();
    LWIP_ASSERT("NetBIOS name is too long!", copy_len < NETBIOS_NAME_LEN);
    if (copy_len >= NETBIOS_NAME_LEN) {
        copy_len = NETBIOS_NAME_LEN - 1;
    }

    /* make name into upper case */
    for (i = 0; i < copy_len; i++ ) {
        netbiosns_local_name[i] = (char)lwip_toupper(hostname[i]);
    }
    netbiosns_local_name[copy_len] = '\0';
}
#endif /* NETBIOS_LWIP_NAME */

/**
 * @ingroup netbiosns
 * Stop netbios responder
 */
void
netbiosns_stop(void)
{
    LWIP_ASSERT_CORE_LOCKED();
    if (netbiosns_pcb != NULL) {
        udp_remove(netbiosns_pcb);
        netbiosns_pcb = NULL;
    }
}

#endif /* LWIP_IPV4 && LWIP_UDP */
